Report a Join on an event without an attendees list as not recorded, and trim redundant comments

backend/services/registration.service.test.js

@@ -866,6 +866,16 @@ describe('registration — a direct sign-up: a Join naming an event itself', ()
     expect(w.logs.error).toEqual([]);
   });
 
+  test('a Join on an event with no attendees collection is NOT recorded, loudly logged — nothing written, nothing notified', async () => {
+    const j = join(PLAIN);
+    const w = setup({ acts: [j], stored: { [PLAIN]: plainEvent(PLAIN, { 'apods:attendees': undefined }) } });
+    await emitJoin(w, j);
+    expect(w.logs.error.some(m => m.includes('NOT recorded') && m.includes('no attendees collection'))).toBe(true);
+    expect(writes(w.calls)).toEqual([]);
+    expect(ledgerOf(w, PLAIN)).toBeUndefined();
+    expect(participations(w)).toEqual([]);
+  });
+
   const readsOf = (w, uri) => w.calls.filter(c => ['pod-resources.get', 'pod-collections.getItems'].includes(c.action) && (c.params.resourceUri ?? c.params.collectionUri) === uri);
   const expectAnonymous = (w, n) => {
     expect(n.recipientUri).toBe(ALICE);